1. Field of the Invention
This invention relates to the use of interleukin-2 (IL-2) in antitumorous cancer therapy.
2. Discussion of the Background:
Attempts have been made recently to develop immunotherapies for the treatment of cancer by stimulating the host immune response to the tumor. These approaches are based on attempts to immunize against specific tumor cells or with nonspecific stimulants in the hope that general immune stimulation would concomitantly increase the host anti-tumor response.
Although some experimental evidence has indicated that this approach might be feasible in the therapy of established tumor, the inability to stimulate sufficiently strong responses to putative tumor antigens and the general immunoincompetence of the tumor bearing host argues against the success of this approach.
An alternative therapeutic approach to the immunologic treatment of cancer is that of the adoptive transfer of immune cells. Adoptive immunotherapy is defined as the transfer to the tumor-bearing host of active immunologic reagents, such as cells with antitumor reactivity that can mediate, either directly or indirectly, anti-tumor effects.
Adoptive immunotherapy represents an attractive approach to cancer therapy and to other conditions related to immune dysfunction. Because active immunologic reagents are transferred to the host, complete host immunocompetence is not required. Thus, the immunosuppression generally associated with a tumor-bearing state does not represent a major problem to this therapeutic alternative. Since host immunocompetence is not required, and in fact could be beneficial to the effects of the adoptive transfer of immune cells, adoptive immunotherapy can be easily combined with other therapies such as chemotherapy and radiation therapy.
Since the transfered reagents are immunologically specific, this treatment modality predicts a high degree of specificity and consequently of low morbidity. Further, in contrast to most other therapies, no immunosuppression is likely to result from this treatment. A review of previous attempts to perform adoptive immunotherapy of cancer in animals and humans can be found in Rosenberg et al, Adv. Cancer Res. 1977; 25:323-388.
Studies have indicated that recombinant interleukin-2 (rIL-2) has notable anti-tumor activity when used alone in tumor-bearing mice. See, for example, Greenberg et al, J. Exp. Med. (1985) 161:1122; North, J. Exp. Med. (1982) 155:1063; Mule et al., Science (1984) 225:1487, and Salup et al., J. Immunol. (1987) 138:641. Recent studies have also indicated that rIL-2 has notable anti-tumor activity in certain human cancer patients. See, for example, Rosenberg et al., N. Engl. J. Med. (1985) 313:1485 and Lotze et al., JAMA (1986) 256:3117. The therapeutic efficacy of rIL-2 also appears to be enhanced when used in conjunction with adoptive immunotherapy (see Mule et al., Rosenberg et al,, and Salup et al., supra).
In humans, the administration of large amounts of rIL-2 induces a variety of severe and dose-limiting toxic side effects (Moertel, JAMA (1986) 256:3141). Therefore, much attention has recently focused on alternative strategies that could exploit the therapeutic benefits of rIL-2 while decreasing the expensive and logistic difficulties associated with adoptive immunotherapy, as well as decreasing the toxic sequelae associated with high dose rIL-2 therapy.
It has been previously noted that Renca murine renal cancer could be successfully treated by a therapeutic regimen that combined doxorubicin and adoptive immunotherapy with rIL-2 (Salup, supra, and Salup, Cancer Res. (1986) 46:3358). This approach offers the advantage of requiring daily adminstration of a moderate amount of rIL-2 instead of the larger amounts required for therapeutic effects with rIL-2 alone. However the discovery of agents, either cytokines, noncytokine biologic response modifiers (BRM), or chemotherapeutic drugs, which can successfully act in concert with moderate amounts of rIL-2 in the absence of adoptive immunotherapy is very much needed.
Recent studies have demonstrated that the adoptive transfer of specifically immune or broadly cytotoxic lymphocytes generated in the presence of human rIL-2 can result in the regression of established tumors in mice and humans. Similarly, the administration of rIL-2 alone, in the absence of adoptive immunotherapy, also has been shown to produce some anti-tumor effects in mice and humans. However, the use of adoptive immunotherapy in rIL-2 to treat cancer patients is a complicated, expensive, and toxic form of therapy.
Flavonoids are benzo-.gamma.-pyrone derivatives which are ubiquitous in plants. Historically, flavonoid-containing preparations have been utilized for the treatment of a variety of human diseases.
These natural compounds have been reported to have pleiotropic biological effects (Havsteen B. Commentary: Flavonoids, a Class of Natural Products of High Pharmacological Potency. Biochem. Pharmacol. 1983; 32:1141-1148). These pleiotropic biological effects include binding to and inhibition of the activity of many biological macromolecules such as vital enzymes. Additionally, some flavonoids have been reported to bind divalent ions of heavy metals, influence the permeability of cell membranes, and intercalate into DNA because of their structural similarity with nucleosides. Since these biological effects could be deleterious to rapidly metabolizing cells, interest has arisen in the potential use of flavonoids as anticancer agents (see, for example, Zaharko et al., Cancer Treat. Rap. 1986; 70:1415-1421, and Corbett et al., Invest. New Drugs 1986; 4:207-220).
Thus U.S. Pat. Ser. No. 4,602,034 discloses (oxo-4-4H-(1)-benzopyran-8-yl) alkanoic acids and their derivatives, represented by the formula: ##STR2## wherein, in the above formula, AR is hydrogen, a phenyl radical which may or may not be substituted, thenyl, furyl, naphthyl, a lower alkyl, cycloalkyl, aralkyl radical, B is a lower alkyl radical, R.sub.1 is hydrogen or a phenyl radical, X is hydrogen or a lower alkyl or alkoxy radical, and n is equal to 1, as well as some salts, esters, amino esters and amides of these compounds.
Fifty-seven specific examples of this class of compounds are reported in U.S. Pat. No. 4,602,034. These compounds are disclosed to be useful in the control of tumors, however their reported anticancer activity is limited to P388 lymphocytic leukemia and carcinoma 38 of the colon.
While some flavonoids may well have direct anti-tumor effects, there is some evidence that one of these compounds can also act indirectly. Finlay et al., J. Natl. Cancer Inst. 1988; 80:241-245, present evidence that the pronounced anti-tumor effects achieved in vivo against Lewis lung carcinoma in mice with flavone-8-acetic acid are not mediated by direct toxicity. Finlay et al. note that the tumoricidal activity of flavone-8-acetic acid was more pronounced and occurs more rapidly in vivo than direct cytotoxic effects observed in vitro.
They also observed that Lewis lung carcinoma cells that were implanted in diffusion chambers in the peritoneum of (DBA/6/J X C57BL/6J)F.sub.1 mice were not susceptible to the effects of flavone-8-acetic acid administered ip. These results were interpreted by Finlay et al. to mean that the anti-tumor effects of flavone-8-acetic acid are not mediated by soluble factors or of metabolites, but rather through stimulation of host cellular anti-tumor activity. Finlay et al. propose that flavone-8-acetic acid mediates at least some of its anti-tumor effects as a biological response modifier.
Some evidence exists in the literature supporting this conclusion. Ching et al., Eur. J. Cancer Clin. Oncol. 1987; 23:1047-1050, have reported that flavone-8-acetic acid augments splenic natural killer activity. Some of the inventors of the present invention have discovered that flavone-8-acetic acid could augment natural killer activity in nonlymphoid organs (liver and lungs) as well as in the spleen, and that flavone-8-acetic acid plus rIL-2 synergistically augmented natural killer activity in normal and tumor-bearing mice (Wiltrout et al. in "The Journal of Immunology", Vol. 140, No. 9, pp. 3261-3625 (1988)). These studies have shown that the combination of flavone-8-acetic acid plus interleukin-2 has synergistic anti-tumor effects for established murine renal cancer in BALB/c mice.
In another publication, Wiltrout et al., J. Natl. Cancer Inst. 1988; 80:220-222, state that preliminary studies have failed to detect induction of interferon or augmentation of natural killer activity by flavone-8-acetic acid in vitro. The authors state that this suggests the possibility that metabolites of flavone-8-acetic acid may be responsible for some of the biological response modifier-mediated anti-tumor effects of flavone-8-acetic acid in vivo, and that this raises the possibility that active metabolites or congeners of flavone-8-acetic acid may be even more effective. In this vein, the authors note that there has already been one clinical trial of another flavonoid compounds, coumarin, a compound of the formula: ##STR3## which has demonstrated anti-tumor activity against selected patients with metastatic renal cell cancer (Marshal et al., J. Clin. Oncol. 1987; 5:862-866). However, in preliminary preclinical experiments performed by some of the inventors (Robert Wiltrout and Ronald Hornung), no therapeutic synergy was observed between coumarin and rIL2.
In view of the wide variety of cancers found in animals, and in particular in humans, there is accordingly a strongly felt need for better regimens of the treatment of different types of cancers.